In gas chromatography and other fields, it is necessary to control the flow of one or more fluids by means of a system of control valves. The configuration of the system may be quite complex, and the valves themselves are often required to be very small and precise in operation. To meet this requirement, the internal volume of the valves should be very small.
Moreover, in many applications all surfaces which come into contact with the controlled fluid must be inert so as to avoid contaminating the fluid. Substances which react with or absorb the controlled fluid can seriously distort the results of a gas chromatography system, for example, since the required sensitivity of those results may be of the order of a few parts per billion, or even less.
It is desirable that the operation of the valves be as simple as possible and that the valves have a long service life (i.e., numerous openings and closures without failure). It is further desirable that valves and connecting channels be integrated into a single inert assembly which is easy to manufacture.
U.S. Pat. No. 4,353,243 to Martin, issued Oct. 12, 1982 describes an arrangement in which a plurality of diaphragm valves are linked by a peripheral channel formed in the surface of a solid plate. While useful in some applications, this system does not have the flexibility of being adaptable to extremely complex arrays and interconnections between a large number of valves.
U.S. Pat. No. 5,083,742 to Wylie, Leveson, Thomson, and Bray issued Jan. 28, 1992 and incorporated herein by reference, describes a fluid control valve for use with chemical fluids where avoidance of contaminants is important. The fluid control valve has a flow control chamber divided into an analytical section and a driver section by a metallic foil operating member, clamped between the peripheral rim of the chamber and the upper wall. The foil membrane is moveable in response to driver fluid pressure between open and closed positions. The upper portion of the rim which engages the membrane is of relatively small surface area, and is made of a softer material than that from which the membrane and the upper wall are constructed, thereby providing a very effective means of sealing the membrane periphery to the upper wall when the assembly is tightly clamped.
U.S. Pat. No. 5,176,359 to Leveson and Bassett, issued Jan. 5, 1993 and incorporated herein by reference, describes a plurality of clusters or pairs of holes extending from one face to the other of a central block selectively interconnected by grooves in the other face of the block. The valves comprise a plurality of blisters formed in a resilient membrane such that the blisters are positioned to coincide with the hole clusters when the membrane is pressed against the face of the block. However, the presence of both membrane sealing faces and grooves in the same block makes manufacturing and implementation of complex valve interconnection schemes more difficult because of the limited area available on the block.